Crosstalk between ferroptosis and chondrocytes in osteoarthritis: a systematic review of in vivo and in vitro studies

Purpose Recent scientific reports have revealed a close association between ferroptosis and the occurrence and development of osteoarthritis (OA). Nevertheless, the precise mechanisms by which ferroptosis influences OA and how to hobble OA progression by inhibiting chondrocyte ferroptosis have not yet been fully elucidated. This study aims to conduct a comprehensive systematic review (SR) to address these gaps. Methods Following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020, we conducted a comprehensive search of the Embase, Ovid, ProQuest, PubMed, Scopus, the Cochrane Library, and Web of Science databases to identify relevant studies that investigate the association between ferroptosis and chondrocytes in OA. Our search included studies published from the inception of these databases until January 31st, 2023. Only studies that met the predetermined quality criteria were included in this SR. Results In this comprehensive SR, a total of 21 studies that met the specified criteria were considered suitable and included in the current updated synthesis. The mechanisms underlying chondrocyte ferroptosis and its association with OA progression involve various biological phenomena, including mitochondrial dysfunction, dysregulated iron metabolism, oxidative stress, and crucial signaling pathways. Conclusion Ferroptosis in chondrocytes has opened an entirely new chapter for the investigation of OA, and targeted regulation of it is springing up as an attractive and promising therapeutic tactic for OA. Systematic review registration https://inplasy.com/inplasy-2023-3-0044/, identifier INPLASY202330044.


Introduction
Osteoarthritis (OA) is the most common form of arthritis (1), affecting 7% of the global human population (2). With the aged tendency of population and higher rates of obesity, the incidence of OA is expected to proliferate (3), which will have a mounting and unavoidable impact on and major challenges for global health care and each country's public health system. For a considerable period, OA has been perceived as a degenerative ailment resulting from mechanical stress. However, there are indications that the inflammation observed in OA is chronic, of a relatively low intensity, and primarily mediated by the innate immune system (4). Due to the intricate and complex onset of OA, its etiology and underlying molecular or inflammatory immune mechanisms remain inadequately elucidated.
Notably, earlier research revealed that cartilage degeneration plays a salient role in the progression of OA (5), while the evolution of OA is associated with oxidative stress and reactive oxygen species (ROS) (6,7). Both the engendering of ROS and the consequent lipid peroxidation are bound up with the antioxidant capabilities of chondrocytes and occupy significant places within cartilage degeneration (8,9). Meanwhile, the breakdown of iron homeostasis and hoard of surplus iron in tissues are linked with oxidative stress, which may cause chondrocytes' injury and damage cartilage homeostasis (10,11). As such, it is of significant interest to probe the role of iron and ROS in the advancement of OA.
Ferroptosis, a novel form of nonapoptotic cell death characterised by the iron-dependent accumulation of lipid hydroperoxides (12), has garnered growing attention over the past decade (13). Recent research has indicated that ferroptosis may participate in immunity, thereby contributing to the regulation of inflammatory damage, signal transduction, and cellular proliferation (14). Based on the aforementioned associations between OA and innate immunity, as well as between ferroptosis and innate immunity, it can be deduced that ferroptosis potentially exerts a significant influence on the etiology and advancement of OA. The ferroptosis of chondrocytes that sparks the progression of OA was initially authenticated by Yao et al. in 2021 (15), and a contemporaneous paper by Jing et al. attested that iron dyshomeostasis is associated with the accelerated progression of OA (16). Shortly afterwards, studies of OA related to chondrocyte ferroptosis began to mushroom, and this has continued over the last two years.
To gain a better understanding of the nexus between ferroptosis and chondrocytes in OA, and to proffer novel insights and unseal a new orientation for in-depth research in both pre-clinical and clinical settings, a rigorous and robust systematic review (SR) is warranted. Based upon the summary of up-to-date in vivo and in vitro research advances, this SR is expected to lay a firm and solid groundwork for future researchers in the realm of OA-ferroptosis. To the best of our knowledge, no SRs concerning ferroptosis and chondrocytes in OA have been published thus far.

Registration and protocol
Systematic Review Centre for Laboratory Animal Experimentation's (SYRCLE) risk of bias tool (18). For cellular experiments, two of the abovementioned authors independently assessed the bias risk table for chondrocyte experiments adapted from previous studies (Table 1) (19). All discrepancies were resolved by discussion and adjudication by a third researcher (HHX).

Data collection and extraction
Information from in vivo and in vitro studies was synthesised narratively and reported using a standardised data extraction form. The following data were collected: author (year), country, cell type and source, animal species, animal age, weight and gender, sample size, core study design, drug delivery approach, duration of intervention, outcome measures and pivotal discovery. One reviewer (SYC) extracted the data, and another (YHW) independently checked their accuracy. Team consensus was sought to resolve any discrepancies.
3 Results and discussion 3

.1 Study selection
In total, 657 records were identified after a comprehensive search of seven databases; these included 142 records in Embase, The selection of chondrocyte cells should be performed from commercially available cell lines or from cartilage samples collected from animals or human patients with consent. In both cases, chondrocytes should be obtained from hyaline cartilage. Control and intervention groups should be clearly defined.
Studies isolating cells from more than one anatomical site were judged to have a high risk of bias.

Selection bias (Confounding variables)
Chondrocytes should be isolated from more than one animal with the same characteristics (type, race, weight and age) from the same anatomical site. Cartilage should be collected from the same anatomical sites, and isolated chondrocytes should have the same viability and count among groups. Studies should implement the same isolation protocol and the same protocol for establishing the primary cell culture(s). The number of cell passages should be the same for all experimental groups and should not be too high, since chondrocytes lose their phenotype with an increasing number of passages. The same experimental conditions and cell density should be guaranteed for both the control and intervention groups.
The studies that did not report the cell density or animal characteristics from which the cells were extracted were judged to have an unclear risk of bias. 3 Performance bias (Exposure measurement) Measurement techniques should be adequate and well-established for the specific outcomes that the studies are assessing, and their measurement protocol should be clearly described to allow for replication. Semi-quantitative and/or qualitative analysis should be performed by two independent observers to ascertain inter-operator reliability.
Studies that did not employ two independent observers for qualitative or semiqualitative analysis were judged to have a high risk of bias. 4 Detection bias (Blinding outcome assessment) The outcome assessor and/or data analyst was not blinded to groups (i.e. intervention vs. control). For quantitative analyses, the blinding of the outcome assessor and/or data analyst was not considered necessary. Otherwise (in semi-quantitative and qualitative analyses), blinding was required.
If no information about performing the semiquantitative analysis blindly was provided, the studies were judged to have a risk of bias.

In vitro studies
An appraisal of risk of bias of the in vitro studies is shown in Figures 3A, B. Among these 20 studies, three (15%) were deemed to have an unclear risk of bias because they did not report whether the chondrocytes were isolated from hyaline cartilage (16,29,38). Just two of the studies (10%) were appraised to have an unclear risk of bias due to 'confounding' because they did not report the cell density or the animal characteristics from which the cells were extracted (25, 33). The bias risk of 18 studies (90%) was considered high in 'exposure measurement' (15, 16, 20-24, 26-31, 34-38), since these studies did not adopt two independent observers for qualitative or semi-qualitative analysis. Nineteen papers (95%) were evaluated as having a high risk in the 'blinding outcome assessment' domain, insomuch as the semi-quantitative analyses were not conducted blindly (15, 16, 20-31, 33, 34, 36-38). Nearly one out of three of the studies (6/20, 30%) were found to have an unclear risk of bias in 'incomplete outcome data' as a result of them not clearly providing information on the number of replicas (15,27,28,34,36,37). All of the 20 studies (100%) were assessed as being at low risk of selective outcome reporting bias, since they presented the results for all the outcomes measured or for all the experimental and control groups. The 'funding bias' domain was appraised to possess unclear risk of bias in three of the studies (15%), since they lacked information on conflicting interests (16,27,29).

In vivo investigations
The results of SYRCLE's risk of bias are depicted in Figures 3C, D. Only two (12.5%) of 16 studies used the random-digit method and were identified as having a low risk of bias in the 'sequence generation' domain (28,35). Moreover, all 16 studies (100%) were judged to have unclear risk of bias because of their absence of information regarding baseline characteristics and the random selection of animals for outcome assessment. Merely two studies (12.5%) adequately concealed the allocation of the animals during the experiment (28, 35). Twelve studies (75%) failed to completely define whether the animals were randomly housed during the experiment (15, 16, 21-25, 27, 29, 33, 34, 37). In the meantime, fourteen studies (87.5%) did not offer opportune blinding of the caregivers/investigators with respect to which intervention each animal attained during the experiment performed or if the outcome assessor was blinded (15, 16, 20-25, 27, 29, 32-34, 37). One study (6.25%) in the 'incomplete outcome data' domain (29) and two (12.5%) in the 'selective outcome reporting' domain were each reckoned to have an unclear risk of bias (15,16). Just one experiment (6.25%) had an unclear risk of bias because it was not reflected in the domains of other bias sources (15).

Panorama of findings
Ferroptosis involved in the pathogenesis of OA have demonstrated that ferroptosis could be a potential target for the treatment of it. Both OA and ferroptosis pertain to intricate pathways that are still not entirely understood. Further research is required to utterly delve into the role of these processes and identify potential interventions to target them with the objective of prevention or remedy. The discoveries of this present up-to-date SR are based on a synthesis and evaluation of the existing 21 studies mainly focuses on two of the three elements of Ferroptosis: iron homeostasis disorder and glutathione peroxidase 4 (GPx4) activity   loss. However, the lipid peroxidation caused by polyunsaturated fatty acids need to be further explored (Figure 4).
From this, chondrocyte ferroptosis acts as a pivotal initiator of OA. The results of the preclinical studies mentioned above have authenticated that the targeted ferroptosis of chondrocytes holds enormous potential for clinical applications and is paramount for a 'precision medicine' approach to the clinical management of OA. During this process, not only do the molecular mechanisms of chondrocyte ferroptosis demand further refinement to identify more treatment targets but the research of ferroptosis inhibitors, the drug delivery system and ferroptotic detection methods are also required to closely meet the development needs.

Regulation of systemic and cellular iron metabolism in the cartilage
In view of abnormal iron metabolism being one of chief features of ferroptosis, six of 20 papers (30%) were focused on iron overload-induced osteoarthritis (IOOA) and ferroptosis. One  research team from Shandong, China, found iron to be involved in the progression of OA, that iron-overloaded mice exhibited greater enhanced cartilage catabolism (16) and that abating iron influx by inhibiting divalent metal transporter 1 (DMT1) activity might be an appealing therapeutic target for OA remedy. The inhibition of DMT1 suppressed interleukin-1b (IL-1b)-induced inflammatory response and ECM degradation via the blockade of mitogenactivated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/nuclear factor kappa-B (NF-kB) pathways. In the same year, the authors followed up with a study revealing that pro-inflammatory cytokines possess the capability to wreck chondrocytes' iron homeostasis, propelling an iron influx (30). Deferiprone, an effective oral iron chelator currently approved by the U.S. Food and Drug Administration (FDA), can easily pass through the cell membrane and efficiently chelate intracellular iron because of its small molecular weight and lipophilic nature (39). Deferasirox (40), another FDA-authorised iron chelator, has efficacy in OA that remains much to be desired. In addition to these, it is also worth trying to employ dexrazoxane and cyclipirox (12). Of note, a combination of iron chelators is better at removing non-proteinbound or free iron than one drug alone (41).
July 2022, one Traditional Chinese Medicine research team revealed that naringenin (NAR) can ease oxidative stress through the nuclear factor-erythroid factor 2 (Nrf2)/heme oxygenase 1 (HO-1) pathway and alleviate cartilage damage under excess iron deposits, which has the potential to cure IOOA (21).
3.6 Activation of the System Xc − /GSH/ GPx4 Axis By generating a stable gene knockdown chondrocyte model, Miao et al. in early 2022 attested that GPx4 downregulation can increase the sensitivity of chondrocytes to oxidative stress, aggravate ECM degradation through the MAPK/NF-kB pathway and subsequently expedite OA progression (28). The staphylococcal nuclease domain containing 1 (SND1) protein was reported in March 2022 to facilitate the degradation of GPx4 by destabilising heat shock protein family A member 5 (HSPA5) mRNA and suppressing HSPA5 expression, promoting ferroptosis in OA chondrocytes (33). As a part of cystine-glutamate antiporter (System Xc -), solute carrier family 3 member 2 (SLC3A2) was shown to be a potential therapeutic target of OA involved in ferroptosis by integrating bioinformatics and experiments in October of the same year (31). After a month, single-cell RNA sequencing analysis revealed transient receptor potential vanilloid 1 (TRPV1) as an anti-ferroptotic target in chondrocytes that abrogated ferroptosis by promoting GPx4 expression (35). The underlying mechanism of mechanical overloading in chondrocytes was described in late 2022 (23). Through Piezo1 channel-mediated calcium influx, mechanical overload induced GPx4-regulated chondrocyte ferroptosis in OA. At the beginning of 2023, the mechanism of ferroptosis resistance in senescent chondrocytes (SenChos) was explored. The excitatory amino acid transporter protein 1 (EAAT1)-glutamate-GPx4 anti-ferroptosis axis was recognised as a critical determinant of SenChos survival (34). Therefore, EAAT1 shows promise to emerge as an efficacious and specific remedial target in OA. He et al. reported that disordered iron metabolism can suppress the expression of collagen II and induce matrix metallopeptidase (MMP) expression by catalysing ROS generation, while biochanin A (BCA) is capable of defending against OA by modulating iron levels and the Nrf2/System Xc -/GPx4 axis (24).
GPx4 is a critical intracellular negative regulator of lipid peroxidation. It utilises glutathione (GSH) to catalyse the conversion of hazardous lipid peroxide into harmless lipid hydroxy and subsequently prevents cells from ferroptosis caused by lipid peroxidation. With the continuous progress made in the investigation of chondrocyte ferroptosis, an increasing amount of evidence has validated that GPx4 is one master chaperon of chondrocyte ferroptosis. Eight out of 21 studies in the present SR involved this key regulator. Thus, targeting GPx4 (e.g. dopamine (42,43), carvacrol (44) and selenium (45)) to modulate chondrocyte ferroptosis may have therapeutic value in the prevention and treatment of OA. What's more, as the central repressor of ferroptosis, GPx4's activity hinges on GSH manufactured from the activation of System Xc -(46).

Detection means of chondrocyte ferroptosis 3.7.1 Existing means
In contrast to other types of programmed cell death (PCD) that have been investigated relatively thoroughly, there is no standardised approach for the detection of ferroptosis. As recapitulated in Tables 2, 3, the most frequently applied methods for detecting ferroptosis include transmission electron microscopy and fluorescent dye to observe the morphology of chondrocytes and organelles (particularly mitochondrion) and detect chondrocytes' viability/toxicity and cellular and histrionic iron levels, lipid peroxidation levels, mitochondrial membrane potential and ferroptosis-related gene expression at both the nucleic acid and protein levels. However, manifold issues remain. At present, the ferroptotic results that have been obtained are mostly descriptive, while it is also possible that other forms of PCD exhibit similar characteristics as ferroptosis. Consequently, the interpretation of these results requires even greater caution. For pre-clinical research, the most critical issue is who is the ultimate executor that enables ferroptosis to occur after lipid peroxidation, which might also contribute to the discovery of additional hallmarks of ferroptosis and significantly differentiate ferroptosis from other forms of PCD. Molecular mechanisms underlying chondrocyte ferroptosis in OA urgently require in-depth investigation to offer ideal and determinant biomarkers.

Burgeoning methodology
Deciphering gene functions is consequential to apprehend the signalling cascades and pathways that administrate senescence and ferroptosis. Modern medicine is striding forward into a new epoch in which advanced and highly integrative functional annotation strategies are being developed to elucidate the functions of all human genes. As a result of advances made in high-throughput technologies, there is a clear trend towards adopting omics analysis in biomedical research to help expound the knotty nexus between molecular layers (47). However, there is a complex crosstalk between different molecules that may have been overlooked by single-omics studies (48). Disease development and clinical presentation can be affected by cross-omics interactions (49,50). A correct verdict can only be reached when diverse assays are integrated in a thorough manner. In the era of precision medicine, multi-omics is an emerging analytical methodology that is expected to provide new insights into the mechanisms involved in disease (48, 51).
Data from multiple omics sources, such as transcriptomics, proteomics and metabolomics, can be integrated to unveil the involute working of systems biology employing machine learning-based predictive algorithms (52). Machine learningbased integration furnishes methods to analyse the various omics data, guaranteeing the discovery of new biomarkers (52). These biomarkers will have the potential to decipher the mechanism of chondrocyte ferroptosis in OA, plumb novel treatment targets and achieve predictive, preventive and personalised medicine at length ( Figure 5).

Future vistas
As previously stated, the primary emphasis in pharmaceutical research pertaining to chondrocytes' ferroptosis centers on the regulation of the two principal components of the ferroptotic network, namely oxidative stress and body iron homeostasis, with minimal attention directed towards lipid peroxidation. The key to ferroptosis is a group of tailored polyunsaturated fatty acid-containing phospholipids. The corresponding lipid peroxides and peroxyl radicals are the execution molecules of ferroptosis. Manipulating lipid peroxidation to suppress chondrocyte ferroptosis can be regarded as an avenue for OA treatment. Acyl-CoA synthetase long-chain family member 4 (ACSL4), the first identified pro-ferroptotic gene product (13), is a member of the ACSL family. Different from other family members, ACSL4 can catalyse arachidonic acid (AA) to synthesise arachidonoyl coenzyme A and then participate in the synthesis of phosphatidylethanolamine (PE). As the main component of phospholipids in cell membranes, PE occupies a significant place in the lipid peroxidation of ferroptosis. Doll et al. confirmed that ACSL4 knockout can significantly inhibit the esterification of AA into PE (53), thereby reducing the susceptibility of cells to ferroptosis and preventing the occurrence of it. As the selective inhibitors of ACSL4, thiazolidinediones (TZDs, e.g. rosiglitazone, pioglitazone and troglitazone) are supposed to restrain OA progression.
It is noteworthy that TZDs is a category of anti-diabetic medications that elicit insulin sensitization in adipocytes by means of activating the peroxisome proliferator-activated receptor-gamma. While OA is one type of the age-correlated joint and bone disorders that are commonly seen in middle-aged and elderly adults (1). These patients also tend to suffer from other chronic diseases, such as diabetes mellitus and cardiovascular and cerebrovascular diseases. From this, we were drawn to consider filtering pharmaceuticals with anti-ferroptosis from existing medicines to fulfil the purpose of 'one drug, multiple illnesses'. Mishima et al. identified various FDA-approved drugs and hormones with anti-ferroptotic properties (54), including rifampicin, promethazine, omeprazole, indole-3-carbinol, carvedilol, propranolol, oestradiol and thyroid hormones. The anti-ferroptotic drug effects were closely associated with the scavenging of lipid peroxyl radicals (54). As a free-radical scavenger, edaravone is thought to reduce oxidative stress and has been used in patients with cerebral infarction as a support therapy for stroke (55). Besides, it can protect against ferroptosis in vitro, as was demonstrated in 2019 by Homma et al (56). Bazedoxifene, a kind of FDA-ratified selective oestrogen-receptor modulator, has been used to prevent and treat postmenopausal osteoporosis (57). Conlon et al. reported in 2021 that bazedoxifene acted as a potent radical-trapping antioxidant inhibitor of ferroptosis both in vitro and in vivo (58). In addition to these findings, it has been affirmed that the hypocholesterolaemic drug probucol and its analogues suppress ferroptosis (59).
Apart from the diverse synthetic chemical drugs sanctioned for commercialization by the FDA as previously stated, natural products, especially those from plants, have been indispensable sources of medication discovery for decades. Many plants' secondary metabolites, such as polyphenols, are increasingly favoured. Due to the structural characteristics of natural compounds, most of them have intrinsic antioxidant activity. Some of them have been confirmed to act as free radical scavengers and lipid peroxidation inhibitors, and thus impede ferroptosis. These natural compounds include quercetin (60), puerarin (61), kaempferide (62), kaempferol (62), gastrodin (63), curcumin (64, 65) and glycyrrhizin (66). There is no denying that such agents will provide invaluable benefits for the treatment of OA.
Despite being distinct from other forms of cell death, it is worth noting that the significant interplay between autophagy and ferroptosis has captured growing attention in recent years ( Figure 6) (67)(68)(69)(70). Such crosstalk might shed important novel light on pharmaceutical research and development of chondrocytes' ferroptosis inhibitors. Oxidative stress and lipid peroxidation products (such as malondialdehyde, ROS, and 4-hydroxynonenal) are powerful inducers of autophagy, while excessive autophagy promotes ferroptosis (68,69). Typically, ferritinophagy, lipophagy, clockophagy and chaperone-mediated autophagy (CMA) facilitate cell predisposition to ferroptosis by degrading ferritin, lipid droplets, aryl hydrocarbon receptor nuclear translocator-like protein 1 (ARNTL) and GPx4, respectively (71). Critical regulators of autophagy such as beclin-1 (72,73), and high mobility group box 1 (HMGB 1) (74, 75) will consequently also have an impact on ferroptosis. Further investigation is required to explore the interplay between ferroptosis and autophagy in the context of oxidative stress, with a view to identify potential targets for synergistic combination therapy aimed at achieving "one drugmultiple targets-OA" for future interventions.
Furthermore, there remains a dearth of research on the optimal parameters for the utilization of chondrocytes' ferroptosis inhibitors, including the conditions of application, time point of onset, dosage, form of administration, and duration of efficacy. Majority of extant studies investigating the pathological effects of ferroptosis have been conducted in animal models and specific cell types, with limited assessment of its clinical safety and efficacy. Thus, further pre-clinical and clinical trials are warranted to elucidate the role of ferroptosis in the human body and establish a foundation for the development of therapeutic agents for the treatment of human diseases.

Novel drug delivery system of OA
As indicated in Table 3, there are several means of administration for in vivo experiments (intra-articular injection, gavage, intra-peritoneal injection and oral administration of drugs in drinking water (20%)). However, orally administered pharmaceuticals are more often than not impeded by side effects (e.g. gastrointestinal symptoms). Considering the closed structure of joints and the limited vascularity of articular cartilage in vivo, intra-articular injection seems to be superior to the effect of oral or intra-peritoneal injection for remedying OA (76), and small molecules are easily cleared by the lymphatic system and blood vessels after being injected into a joint cavity (77,78). A high clearance rate will inevitably entail a drug's failure to reach its remedial dose. For effective therapy, multiple and frequent administrations are required. Multiple injections of fluid into a joint may increase the risk of inadvertent joint infection, which greatly curbs this type of administration. To date, more than 70% of the current market drugs and recently discovered drugs have been found to have poor water solubility (79). In the foreseeable future, a major challenge for the pharmaceutical industry will be to enhance the solubility of active pharmaceutical ingredients (80). To release drugs controllably, enhance the half-life of drugs and promote the repair of cartilage injury, it is necessary to develop novel sustainedrelease drug delivery systems (DDS) for OA (Figure 7). Hydrogels, one kind of three-dimensional networks of crosslinked hydrophilic polymer with good biocompatibility, have for years been widely used for biomedical applications (81)(82)(83). However, before hydrogels can see widespread use and clinical translation, several deficiencies must be to be addressed, including their weak mechanical properties and compromised bioactivity (84). The great potential of nanomedicine for cartilage repair has brought a new dawn to cartilage tissue engineering. Nanocomposite hydrogels can markedly mimic natural cartilage components with excellent histocompatibility, exhibiting unique biological effects (85). In view of this, the number of investigations on nanocomposite hydrogels has risen steeply. A combination of nanoparticles (NPs) and hydrogel offers a variety of synergistic properties superior to their individual ones, and in the meantime, the rehabilitative capacity of cartilage has apparently been boosted (86,87). In addition to nanocomposite hydrogels, NPs themselves have also been widely investigated for the treatment of bone-related diseases due to their special characteristics (88). The application of NPs for DDS can not only prolong the in vivo retention time of drugs but also bolster the biodistribution and fulfil the aim of passive and active targeting at the diseased site (88, 89).

Limitations
This SR has several limitations. The first limitation is that the studies it includes were all carried out in cellular or animal models, which hardly mirror the proceedings occurring within humanity. Secondly, the studies embraced manifold designs and approaches, which may make it challenging to compare their results. It is rewarding to note that the mechanisms latent in the link connecting chondrocytes, ferroptosis and OA are likely sophisticated and multi-dimensional. Thirdly, the quality assessment using the risk of bias tool found that critical details regarding the design and conduct of the included experiments were missing. Accordingly, most studies were unable to estimate the risk of bias. As a major concern, the absence of vital methodological details may indicate neglect in using these methods, potentially inducing skewed results (92). Moreover, it is likely that pertinent studies may still have been omitted, although seven cardinal electronic databases were employed to identify potential studies. Given the circumscribed size of the existing study, follow-up indepth investigations are exceedingly worthy and pressing. In addition, nearly all studies (20/21, 95.23%) originated from China, leading to possibly poor extrapolation of the findings. Finally, the inclusion of the published studies and the exclusion of non-English studies undeniably renders selection bias.

Conclusion
As described previously, the pathogenesis of OA is complex, and existing treatments that target its symptoms are often insufficient. As a result, exploring the pathogenesis and seeking new targets have formed the new breakthrough point for the prevention and control of OA. Gratifyingly, there is copious evidence for ferroptosis to be set as a promising therapeutic target for disease-modifying interventions in OA. Moving forward, there remain pressing challenges and inquiries that require attention. Current knowledge of chondrocyte ferroptosis in OA is possibly only the tip of the iceberg, and investigations pertaining to it are still in their infancy. In terms of pre-clinical investigation, the crux is identifying the definitive agent responsible for facilitating ferroptosis subsequent to lipid peroxidation, as well as determining the optimal biomarker for the prevention or prognosis of OA.
Accordingly, comprehending the network organization of the ferroptosis system, as opposed to the impact of individual regulators, assumes greater significance in gaining a profound understanding of the mechanisms that underlie ferroptosis. Elucidating the ferroptotic network will also furnish valuable insights into the diagnosis and treatment of OA. Therefore, FIGURE 7 Potential intra-articular administration in the remedy of osteoarthritis animal models. Local administration of pharmaceuticals assuages the progression of OA in the in vivo model. Bioactive materials (e.g., hydrogels, NPs, CBNPs, and nanocomposite hydrogels) loaded with drugs mimic the ECM microstructure and improve medicine-release properties, therefore advancing OA rehabilitation and rebuilding efficacy. CBNPs, cell membrane biomimetic nanoparticles; NPs, nanoparticles.
additional research is necessary to uncover the latent mechanisms that underlie ferroptosis in the onset and progression of OA. It is anticipated that more efficacious and suitable strategies for treatment and prophylaxis will emerge in the foreseeable future.

Data availability statement
The original contributions presented in the study are included in the article/Supplementary Material. Further inquiries can be directed to the corresponding authors.